Soluble Electroluminescent Poly(phenylene vinylene)s with Balanced Electron- and Hole Injections
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- 作者：Yuh-Zheng Lee ; Xiwen Chen ; Show-An Chen ; Pei-Kuen Wei ; and Wun-Shain Fann
- 刊名：Journal of the American Chemical Society
- 出版年：2001
- 出版时间：March 14, 2001
- 年：2001
- 卷：123
- 期：10
- 页码：2296 - 2307
- 全文大小：276K
- 年卷期：v.123,no.10(March 14, 2001)
- ISSN：1520-5126
文摘
We report a new route for the design of efficient soluble electroluminescent PPV-based copolymersbearing electron-deficient oxadiazole (OXD) moieties on side chains. The introduction of OXD through along alkylene spacer with PPV backbone provides a molecular dispersion of OXD in the film; both the sidechain OXD and the main chain PPV do retain their own electron-transport and emissive properties, respectively.The use of phenylene vinylene derivatives with asymmetric and branched substituents and a long spacer providessolubility for ease of device fabrication as well as amorphous structure to allow a well-mixing of OXD groupswith the main chains. By properly adjusting the OXD content through copolymerization, we can tailor thechemical structure of electroluminescent material to give a balance of hole- and electron injections for variousmetal cathodes, such that the quantum efficiency is significantly improved and the turn-on voltage is reducedfor the devices with aluminum and calcium. For the device with calcium fabricated in open air, a maximumbrightness of 15000 cd/m2 at 15 V/100 nm and a maximum luminance efficiency of 2.27 cd/A can be obtained,respectively, about 30 times brighter and 9.4 times more efficient than those with the correspondinghomopolymer, poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV). The use of physicalblends to simulate the copolymers provides no significant improvement, since phase-separation structures appear,causing an inefficient utilization of OXD and sometimes voltage-dependent emission spectra. The presentroute permits a fabrication of single layer PLED with high brightness, high efficiency, and low turn-on voltage.